High-resolution ẟ18O and ẟ2H profiles from 700 to 800 kyr BP in the Beyond EPICA ice core: insights from a comparison with EPICA Dome C

The Beyond EPICA project (BE-OI) has extended the oldest continuous ice core climate record, capturing at least 1.2 million years. The 2,800-meter-long core was drilled at Little Dome C (LDC) in the East Antarctic Plateau, 35 km south-east of Dome C (DC). BE-OI seeks to disentangle the Mid-Pleistocene Transition (0.9-1.2 Myr BP), a crucial period of Earth’s climate history when the shorter 41 kyr glacial cycles shifted to a dominant 100 kyr regime.Paleotemperature reconstructions obtained from ice cores mainly rely on water stable isotopes (ẟ18O and ẟ2H). Variations in isotope ratios reflect changes in local temperature with less negative values characterizing warmer periods and more negative values associated with colder conditions. Past interglacial periods characterized by higher temperatures, higher sea levels, and reduced ice sheets provide valuable insights for investigating how different orbital configurations affect the climate system without the influence of northern hemisphere glacial ice sheets.Within this framework, a preliminary comparative analysis was carried out between EPICA Dome C (EDC) and Beyond EPICA isotope records, with a focus on the climate variability between 700 and 800 kyr BP. This period covers two interglacials corresponding to the bottom part (3082-3189 m) of the EDC ice core including MIS 19 which represents the period with the closest orbital configuration parameters to the Holocene. In this study, high-resolution measurements of ẟ2H and ẟ18O were performed by means of Cavity Ring-Down Spectroscopy. Sample analyses were conducted with a sampling resolution of 2.5 cm using internal standards intercalibrated within the laboratories of the Beyond EPICA water isotope consortium. This high-resolution record is in good agreement with the low-resolution isotopic measurements performed in the field. The captured climate variability has been compared with the EPICA record to assess the onset of potential new climatic information captured by water stable isotopes. To account for the differences between the two coring locations, the stable isotope composition of surface snow collected along an initial traverse between DC and LDC during the 2023–2024 field season will be considered, together with snow trench samples from both sites.